1. Field of the Invention
The present invention relates to a personal watercraft in which a deck is assembled onto a hull to constitute a watercraft body. An engine is mounted in a space surrounded by the watercraft body. Furthermore, an intake system of the engine is provided with a vertically elongated air box.
2. Description of Background Art
A personal watercraft is known from, for example, Japanese Patent Laid-Open No. Hei 8-48287 entitled xe2x80x9cPERSONAL PLANING WATERCRAFT.xe2x80x9d FIG. 1 of the above publication has been reproduced as FIG. 7 of the present invention. It should be noted that the reference numerals have been re-assigned in FIG. 7 to avoid confusion with FIGS. 1-6 of the present invention.
Referring to FIG. 7, a sectional view of the personal watercraft of the above publication is illustrated. The personal watercraft 100 has a structure in which left and right side walls 102 and 103 are provided at substantially central portions of a deck 101. A saddle ride type seat 104 is provided at the upper ends of the left and right side walls 102 and 103. An engine 105 is disposed on the lower side of the seat 104, directed in the front-rear direction of a watercraft body 106. In addition, intake system equipment 108 is provided in a space on the left side of the engine 105.
The intake system equipment 108 has a structure in which an intake silencer 108b is in communication with cylinders 105a of the engine 105 through air funnels 108a. An intake pipe 108c is in communication with the intake silencer 108b. According to the intake system equipment 108, air sucked into the intake pipe 108c through a suction port 108d of the intake pipe 108c can be led into the intake silencer 108b. The air led into the intake silencer 108b can be introduced into the cylinders 105a through the air funnels 108a. 
However, the intake pipe 108c is horizontally extended rearwards from a rear wall of the intake silencer 108b and towards the center 106a of the watercraft body 106. The lower end 108e of a connection portion for connecting the intake pipe 108c to the rear wall of the intake silencer 108b is located above a bottom surface 108f of the intake silencer 108b. With this structure, if sea water or water should penetrate into the intake silencer 108b, the sea water or water would accumulate in the intake system equipment 108, particularly in the intake silencer 108b. 
In addition, sea water or water may penetrate into the watercraft body during operation of the personal watercraft. If sea water or water penetrates into the watercraft body, the sea water or water may penetrate into the cylinders 105a through the air funnels 108a. Therefore, it has been desired to put into practical use a personal watercraft 100 in which the penetration of sea water or water into the cylinders 105a can be prevented even if the sea water or water penetrates into the watercraft body 106.
Accordingly, it is an object of the present invention to provide a personal watercraft in which sea water or water can be prevented from accumulating in intake system equipment and in which penetration of sea water or water into an engine can be prevented even if the sea water or water penetrates into the watercraft body.
In order to solve the above problems, a first aspect of the present invention is directed to a personal watercraft, which includes a watercraft body comprised of a combination of a hull constituting a lower portion of the watercraft body and a deck constituting an upper portion of the watercraft body. An engine is mounted in a space surrounded by the watercraft body. An intake system of the engine is provided with a vertically elongate air box. An air suction port for sucking in air is provided at a lower portion of the air box. Furthermore, the inlet of an air passage for leading air from the air box to the engine is opened in the upper half of the air box.
The intake system of the engine is provided with the air box, and the air suction port for sucking in air is provided at the lower portion of the air box. With this structure, even if the personal watercraft is turned upside down and sea water or water penetrates into the air box, the sea water or water in the air box can be drained through the air suction port by restoring the personal watercraft to the normal posture.
In addition, with the inlet of the air passage for leading air to the engine opened in the upper half of the air box, the inlet of the air passage can be located at a high position. With this structure, even if sea water or water penetrates into the watercraft body, the sea water or water can be restrained from rising up to the inlet of the air passage.
A second aspect of the present invention includes an air filter provided between the air suction port and the inlet of the air passage. The interior of the air box is partitioned by the air filter into upper and lower portions.
With the air filter provided between the air suction port and the inlet of the air passage, air sucked in through the air suction port can be led to the inlet of the air passage through the air filter. Accordingly, dust and the like contained in the air can be removed by the air filter, so that clean air can be led to the inlet of the air passage.
A third aspect of the present invention includes a cut-off wall provided on and surrounding a top plate of the air box. The cut-off wall is provided with a cutout portion for draining water at a portion away from the air suction port.
With the cut-off wall provided along and surrounding the outer periphery of the top plate constituting the air box, a recessed portion can be formed by the outer periphery of the top plate and the cut-off wall. Therefore, sea water or water splashed onto the top plate can be led to the recessed portion. Furthermore, with the cut-off wall provided with the cutout portion, the cutout portion can be in communication with the recessed portion. Accordingly, the sea water or water led to the recessed portion can be drained through the cutout portion.
In addition, with the cutout portion formed at a portion away from the air suction port, the sea water or water drained through the cutout portion can be prevented from splashing onto the air suction port.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.